Prototyping Your Way out of a Mess

A Simple Product with Tricky Design Aspects

The latch on the left side of the Dotz CordIdentifier looks like it would require a typical side action mold, but it is actually formed by a pass-through core from the A-side mold half. As the mold closes, that A-side core forms a shutoff against the surface of the B-side mold half. The three-degree draft of that feature prevents entrapment of the mold feature as the mold opens, forming the side-facing opening without the use
of a side action. The draft also keeps the mold surfaces from abrading one another as the mold opens.

The living hinge in Maraia's design is also nicely done. Some living hinges don't precisely align their bends, leaving the meeting of the hinged parts uncertain. On this part, a wedge-shaped ridge along one side of the hinge fits perfectly into a corresponding groove on the other side of the hinge. This ensures precise alignment of the two halves of the part, and helps align the clip on the right half of the part with the mating catch on the left.

One of the trickiest aspects of this design is the articulated parting line, along which the two mold halves meet. In particular, it’s the "teeth" along the edges of the part that are trickiest from the mold design aspect. These teeth are designed to clamp onto cables of varying sizes to keep the cord identifier in position once it has been put in place. They were designed to flex slightly, to hold the cable firmly without damaging it.

The parting line of the mold goes up and down following the contours of the teeth, requiring some very smart design on Maraia's part to allow for such a complex structure without interfering with molding or ejection. The teeth are spaced and drafted properly to allow the milling tools to cut the relatively narrow mold features that will form them and allow the finished part to be cleanly ejected from the B-side mold half. The A-side mold surface is flat and smooth where it forms the outer surface of the teeth. The spaces between the teeth are formed by protrusions of the B-side mold half, which shut off against the surface of the A-side mold half. These shutoffs are drafted to prevent flash, allow clean mold opening, and prevent damage to the mold.

Maraia's choice of polypropylene resin provides the clear window for the paper icon, but it also flows well, which is important in a complex design like this one.

The rise of PLM and end-to-end tool chains which essentially facilitate feedback (implementation of engineering changes after the initial prototyping phase) is a very important aspect of this process. We're going to explore this further in an upcoming edition of Design News Radio. Please click on the link to register: Bridging the Mechanical & Embedded Design Worlds.

I agree that the living hinge and the snap-togather are very critical features that would demand a lot out of any prototype. So I am impressed that it worked well. I would offer an opinion that icons are stupid and numbers would be a far more universal method. Also, probably easier to read in poor light, if an appropriate font and size were used. Numbers plus colors could easily provide at least 40 discrete identities, which should be enough for most folks. Hopefully the buttons can be opened for removal and re-use, and to correct installation errors. This would be the best point in competing against the non-reusable cable ties that are also used for cable identification.

Wonderful idea. Using a color piece at both ends of the cord may preclude the need for an image. In many places in my house, it would be difficult to see the image (under the TV cabinet). But the color would be easy to spot. If there were a corresponding color doohicky at the appliance end, the image wouldn't be necessary.

Interesting story of what appears to be a high utility product. Just goes to show you what seems simple in terms of concept and even design, doesn't necessarily translate that way when it comes to exploring the optimal manufacturing and production methods. This is a nice example of how prototyping services priced within reach can give even the bootstrapping inventor an actual chance of bringing product to market. Nicely done, Micah.

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.